The variolins are a class of marine alkaloids isolated from the rare, difficult to access Antarctic sponge Kirkpatrickia varialosa, with variolin B (1) being a typical example. The variolins all contain a fused pyrido[3′.2′:4.5]pyrrolo[1.2-c]pyrimidine core (2), with either a heterocyclic aromatic ring or an ester group attached at C5, as in variolin B (1), variolin D (3) and deoxyvariolin B (4).

The variolins are disclosed to have antitumor activity and other useful properties. The complete structure for these and related compounds is given by N. B. Perry et al., Tetrahedron 1994, 50, 3987-3992 and G. Trimurtulu et al., Tetrahedron 1994, 50, 3993-4000.
Synthetic studies towards the 2-aminopyrimidine alkaloids variolins and meridianins are the subject of Tetrahedron Lett. 2000, 41, 4777-4780. M. Alvarez et al., Tetrahedron Lett. 2001, 42, 315-317 describe a synthesis to deoxyvariolin B starting from 7-azaindole. Studies towards the total synthesis of the variolins are described in Tetrahedron Lett. 2001, 42, 311-313. The first total synthesis of variolin B was described by R. J. Anderson et al. Tetrahedron Lett. 2001, 42, 8697-8699. Later, P. Molina et al. Tetrahedron Lett. 2002, 43, 1005-1007 also described the synthesis of variolin B achieved by tandem aza-Wittig/carbodiimide cyclisation.
WO 0204447 published 17 Jan. 2002 describes a method for preparation of variolin B (1) and deoxyvariolin B (4) from simple monoheteroaromatic starting materials, along with providing new variolin derivatives.
WO 0212240 published 14 Feb. 2002 relates to derivatives of variolin B.